1. Field of the Invention
The present invention relates to a liquid transfer device and manufacturing method thereof.
2. Description of Related Art
There has been widely used in various fields liquid transfer devices each of which includes a common liquid chamber and individual passages branching off from the common liquid chamber and which transfers liquid by applying pressure to liquid in the individual passages. Among these liquid transfer devices is a liquid transfer device whose passage unit has liquid passages including a common liquid chamber and individual passages are formed by laminating a plurality of plates each having holes constituting liquid passages.
Japanese Unexamined Patent Publication No. 25636/2004 (Tokukai 2004-25636) discloses the following ink-jet head, particularly with reference to FIG. 6. Namely, the ink-jet head has a passage unit having ink passages. These ink passages include a common ink chamber and individual ink passages. Each individual ink passage branches off from the common ink chamber and connects to a nozzle, via a pressure chamber. From the nozzle are ejected ink droplets. The passage unit of the ink-jet head is formed by laminating the following plates: a synthetic resin plate having nozzles; and a plurality of metal plates having holes constituting ink passages which lead to the nozzles. The ink passages are constituted by pressure chambers, common ink chambers and the like. The publication discloses that the plates are bonded with one another by applying an adhesive to the plates and applying heat and pressure in the direction of laminating the plates (the direction is hereinafter simply referred to as “laminating direction”).
Japanese Unexamined Patent Publication No. 22137/2005 (Tokukaihei 2005-22137) discloses an ink-jet head having a passage unit formed by laminating a plurality of plates having holes constituting the ink passages. To bond these plates with one another, the publication describes dispersing of metal atoms among the plates, in addition to application of a high pressure in the laminating direction under a high temperature conditions.
Among the ink passages formed in the passage unit, the common ink chamber which branches into individual ink passages and serves as the source of ink supply is required to have a relatively large capacity to retain a large amount of ink. For this reason, the hole(s) constituting the common ink chamber (hereinafter simply referred to as “the hole(s)”) in general have a relatively large opening area. Therefore, when a pressure is applied to the plates in the laminating direction as in the cases of the above two publications, the pressure may cause deformation in a side wall defining the hole. The deformation may further leads to a problem of insufficient bonding between the plates. These problems are particularly noticeable when the plates are bonded with one another by metal diffusion bonding as in the latter case, because metal diffusion bonding requires application of a considerably high pressure.
In view of that, in the latter case, the opening area of the holes on manifold plates are made different from one another in such a manner that a manifold plate in an upper layer in the laminating direction has a smaller hole than one in the lower layer. This restrains the above described pressure-caused deformation.